Method of drying and initial input control for modulated gas dryer



May 30, 1967 .1. P. LUX 3,322,415

METHOD OF DRYING AND INITIAL INPUT CONTROL FOR MODULATED GAS DRYER FiledJan. 5, 1965 2 Sheets-Sheet 1 TEMPEQA TUEE INVENTOR. dose 0 r? 460:

ATTQRNEYS ISY May 30, 1967 P LUX 3,322,415

- J. METHOD OF DRYING AND INITIAL INPUT CONTROL FOR MODULATED GAS DRYERFiled Jan. 5, 1965 2 Sheets-Sheet 2 (Jose ob P 4 ax ATTORNEYS UnitedStates Patent Corporation, Benton Harbor, Mrch., a corporation ofDelaware Filed Jan. 5, 1965, Ser. No. 423,447 6 Claims. (Cl. 263) Thepresent invention relates to heating systems, particulanly to gas firedheating systems for clothes dryers.

Typically, the length of a drying cycle in a clothes dryer ispreselected by means of a timing mechanism, the operator having theoption to select different drying cycles for different types of fabrics.This type of system is not entirely satisfactory since the correctdrying time can vary substantially as between two loads of fabrics ofthe same general character.

Some improvements in operation are effected by providing a dryerassembly in which the supply of fuel gas to the burner is varied ormodulated in response to the dryer drum air or exhaust air temperature.A system of this type has been described in the Fleer et al. US. PatentNo. 3,084,865 issued Apr. 9, 1963. While the control device shown inthis patent works reasonably well with ordinary fabrics, experience hasshown that it may not be satisfactory for the drying of delicatefabrics, particularly those containing synthetic resins. This is due tothe fact that there is a substantial time lag between the initialignition of the burner at the start of the cycle, and the time at whichthe temperature responsive device in the exhaust of the dryer takes overand controls the inlet of gas to the burner. During this interval, theinlet temperature to the dryer drum may become quite high While theexhaust air is still at a moderate temperature. Such execessive inlettemperatures may lead to softening and even fusion of fabrics containingsynthetic fibers.

One of the objects of the present invention is to provide an improvedheating system for clothes dryers with a dual control, one of which isresponsive to the exhaust temperature, while the other is responsive totemperatures in proximity to. the burner to control the temperatureshortly after the burner is ignited.

Another object of the present invention is to provide an improvedtemperature control system for gas-fired clothes dryers and the likeemploying a pair of cooperating heat sensing elements which modulate thegas input to the burners to control the warm up time in the dryer so asto prevent scorching or fusing of delicate fabrics.

Still another object of the present invention is to provide an improvedcontrol system for gas fired burners which is relatively inexpensive andfoolproof in operation.

A further description of the present invention will be made inconjunction with the attached sheets of drawings in which:

FIGURE 1 is a somewhat schematic view of a clothes dryer embodying theimprovements of the present invention;

FIGURE 2 is a cross-sectional view of the gas burner control of thepresent invention;

FIGURE 3 is a graph illustrating temperature versus time at differentlocations in the dryer; and

FIGURE 4 illustrates a modified temperature sensing means which can beemployed in another form of the present invention.

As shown in the drawings:

In FIGURE 1, reference numeral 10 indicates generally a gas firedclothes dryer including a rotatable drum 11 therein, with an access door112 being provided for introducing fabrics into the interior of the drum11. The drum 11 rotates about a shaft 13 on which is mounted a pulley14. A suitable drive belt connects the pulley 14 to a drive motor (notshown). The periphery of the drum 11 is supported for rotation on spacedrollers 16 secured to a base 17 of the machine. Another pulley 18 isalso driven by a suitable motor (not shown) and operates a blower 19 todirect heated air from the interior of the drum 11 through an exhaustgenerally indicated at reference numeral 21.

The burner 22 fed from a gas line 23 provides the heat necessary fordrying the fabrics in the drum 11. The control of the gas feed from thegas line 23 to the burner 22 is accomplished by means of a control unitwhich is illustrated generally at reference numeral 24 in FIGURE 1, andwhich is more fully shown in FIGURE 2.

The control system of the present invention includes a pair oftemperature responsive sensors 26 and 27, the former being positioned inthe exhaust 21, and the latter being positioned in proximity to theburner 22. For best results, the sensor 27 is not located directly inthe flame of the burner, but in sufficiently close proximity so that itresponds quickly to increases in temperature at the burner. The sensor26 includes a bulb 28 filled with a readily expansible liquid such asxylene, and is connected to the control unit by means of a line29. Thesensor 27 also includes a bulb 31 connected to the control unit 24 bymeans of a line 32.

Turning now to FIGURE 2, it will be seen that the control unit 24includes a valve body portion '36 having a threaded inlet 37 forreceiving the gas supply line 23 in threaded engagement. Gas flow to theburner is controlled by the operation of a solenoid valve having atapered valve seating face 38 arranged to seat against a resilient valveseat 39. The valve face 38 is attached to an armature 41 arranged forreciprocation along the axis of a solenoid coil 42. A spring 43 urgesthe valve face 38 into seating engagement with the seat 39, andenergization of the solenoid unseats the valve face 38 from the valveseat 39 to permit gas flow from an inlet passageway 43 to a passageway44.

Threadedly secured to the valve body 36 is a tube 46 which extends intothe inlet 47 of the burner 22. At one end of the tube 46 there isprovided a shouldered orifice plug 48 which has a cylindrical outletbore 49 and an enlarged frusto-conical bore 51 communicating therewith.A valve element generally indicated at reference numeral 52 is arrangedto be received in varying positions within the combined bores 51 and 49and thereby meter the amount of gas flow entering the burner 22. Thetype of valve element shown in FIGURE 2 is more completely described inFleer et a1. Patent No. 3,084,865 issued Apr. 9, 1963. The valve element52 has a conically pointed end portion 53 whose base diameter is largerthan the diameter of the cylindrical bore 49, and the included angle ofthe conically pointed end portion 53 is the same as the included angleof the frusto-conical bore 51 so that the tapered surface of the conicalpoint and the wall of the bore 51 engage in seating relation as thevalve element is moved toward the orifice. The tapered end ofv the valveelement 53 is provided with a longitudinally extending flat surface 54which permits a certain amount of gas to bleed through the bore 49 whenthe valve element 52 is seated and provides for varying the flow of gasproportional to the axial movement of the valve 52.

The valve element 52 has a reduced diameter stem 56 which is receivedthrough an apertured guide plate 57 so that the tapered end of the valveelement 52 is slidably guided by the frusto-conical bore 51. Near theend of the stem portion 56 there is provided a collar 58. A spring 59extends between the collar 58 and one face of the plate 57 to urge thevalve element 52 out of seating relation with the bore 49. The end ofstem 56 is threaded and receives a threaded adjustment nut 62 theposition of which governs the closing of the valve as will be apparentfrom the subsequent disclosure. A flat leaf spring 61 is secured to thevalve element 52 to bias the valve element transversely to make surethat the conical end portion 53 will be engaged with the wall of theconical bore 51 and prevent vibration of the valve element in theassembly.

The position of the valve element 52 with respect to the bores in theplug 48, is controlled in one instance by a pivoted lever generallyindicated at reference numeral 64. The lever 64 includes one arm 63having an aperture 65 through which the threaded end of stem 56 extends.Arm 63 is normally spaced from adjustment nut 62, but upon an increasein exhaust temperature above a pre determined point, the arm 63 engagesnut 62 by means of operation of mechanism hereinafter described. Thelever 64 is pivoted at a pin 66 and has a shorter arm portion 67engaging a pushrod 68 of the temperature responsive device. The latterincludes a rigid outer housing 69 secured to the valve body 36 by meansof fastening means 71. Inside the rigid wall 69 there is a flexible wall72 bearing against a headed end 73 of the pushrod 68. A spring 74normally urges the headed end 73 against the flexible wall 72. When thetemperature rises in the exhaust 21, however, the expansion of theliquid within the bulb 28 and the conduit 29 and contained in anexpansion chamber 76 behind the flexible wall 72 exerts suflicientpressure on the flexible wall 72 to move the pushrod 68 to the left asseen in FIGURE 2, thereby pivoting the lever 64 in the counterclockwisedirection about the pivot pin 66. The resulting pivotal movement of thelever moves arm 63 into engagement with nut 62 and thereby moves thevalve element 52 to the right as shown in FIGURE 2 and decreases theeffective area through which the gas can flow to the burner 22.

The system described thus far is one which is commonly used for makingthe gas feed to the burner responsive to exhaust temperatures. However,such a system is subject to the previously mentioned disadvantage thatdelicate fabrics might be scorched or even fused while the exhausttemperature is being built up to the point where the temperatureresponsive device can reduce the gas flow to the burner. To overcomethis difficulty, the present invention provides a second temperaturesensing means responsive to temperatures in close proximity to theburner 22. The bulb 31 is positioned fairly close to the burner 22, butnot directly in the flame. The conduit 32 connected to the bulb 31 feedsinto an expansion chamber 78 located on one side of a flexible wall 79confined within a rigid wall 81. A pushrod 82 having a headed endportion 83 bearing against the flexible wall 79 is responsive tomovements of the flexible wall 79 due to the thermal expansion of theliquid contained within the bulb 31, the conduit 32 and the expansionchamber 78. A spring 84 normally urges the headed end 83 against theflexible wall 79. Spring 84 is of suflicient strength to overcome thebiasing force of spring 59. The opposite end of the pushrod 82 isconnected by means of a pivot pin 85 to a lever 86 pivotal about a pivotpin 87.

The free or lower end 88 of lever 86, as seen in FIG- URE 2, is inregistry with the end of stem 56 and abuts a rounded end 85 formed onthe stem 56 so that pivotal movement of lever 88 may effect movement ofthe valve element 52 either to the right under the force of spring 84 orto the left by expansion of the liquid in bulb 31 which overcomes spring84 and allows spring 59 to move valve element 52 to the left.

In modulated gas systems of the type described in the Fleer et a1.United States Patent No. 3,084,865 issued Apr. 9, 1963, the gas controlvalve is in its fully open position at the start of operation andgradually closes in response to an increase in a sensed controltemperature at one point in the system to be controlled. In accordancewith the principles of this invention the gas control valve is in atleast a partially closed position at the start of operation and firstmoves to a more open position under the influence of a first controltemperature followed by a gradual closing under the influence of asecond control temperature.

Referring to FIGURES l and 2 wherein the control unit 24 is shown in itsoff or cold position the operation of the control mechanism of thesystem is as follows. The dryer motor is energized to drive the blowerand the tumbling drum and at the same time burner 22 is ignited. Sincethe control valve is in a partially closed position the burner willsupply heat at a reduced input. However, even at reduced heat input thesensing bulb 31 is heated to the point where the liquid therein expands.As the liquid in bulb 31 expands pushrod 82 is forced to the right asviewed in FIGURE 2. This movement of pushrod 82 to the right, moves thefree end 88 of the lever 86 to the left as viewed in FIGURE 2 and allowsstem 56 to move to the left under the influence of spring 59. Thus thecontrol valve begins to open allowing more gas to reach burner 22 andincreasing the heat input to the dryer. Obviously, as more and more heatinput is supplied, the bulb 31 will be heated more and more causing moreand more expansion of the liquid within the bulb which in turn allowsincreased opening of the control valve. Opening of the control valvewill continue until stem 56 moves to a position where nut 62 engageslever 64. At this time, if sensing bulb 28 has been heated to the pointwhere it is effective to move pushrod 68 to the left as viewed in FIGURE2, the lever 64 will be effective to begin closing the control valve aspreviously described. The remainder of the drying cycle proceeds as inthe prior art systems.

A graphical representation of the temperature conditions involved in thedryer will be found in FIGURE 3 of the drawings. In that figure, graph Ais a representative plot of the temperature at the exhaust in the priorart systems. In the absence of the inlet control tem perature sensed bythe bulb 31, the temperature in the drum adjacent to the burner 22 wouldrise rapidly as indicated in curve B, and would then taper off when thevalve element 52 came under the control of the temperature sensingelement located in the exhaust 21. As a result of the addition of theinlet temperature sensor, the temperature adjacent the burner isrepresented by the graph C, and includes a moderately rising initialportion which exists until such time as the bulb 31 is heatedsufficiently by the burner 22 to actuate the valve element 52. Then, therise in temperature is much more rapid and ultimately, the temperatureis decreased along a gradually decreasing slope by the action of theexhaust sensing element. Graph D represents the exhaust temperature inrelation to time in a dual sensor system. The rise in exhausttemperature is much more gradual than in a single sensor system, buteventually catches up after the danger of high inlet temperatures haspassed. With this type of temperature-time relationship, there is notendency to scorch or fuse the fabrics, and drying proceeds under morecarefully controlled conditions than exist in the absence of the secondsensing means.

It is not necessary that the second sensing means, represented by thebulb 31, be located physically in close proximity to the burner 22. Asillustrated in the form of the invention shown in FIGURE 4, the bulb 31is surrounded by an electric heating coil 97, and can be positionedremotely from the burner 22. The function of the heating coil 97 is toprovide suflicient heat to the bulb 31 to open the control valve beforethe regulation afforded by the bulb 28 comes into effect, to therebycontrol operation of the valve element 52 in the interval betweeninitial ignition of the burner, and the time when the exhaust sensortakes over.

While the principle of system operation remains the same withindependent heating means it will be evident that by providing a heatingmeans for bulb 31 which is not responsive to the temperature of theburner 22, opening of the control valve may be regulated to give a morenearly stragiht line temperature to time relationship as illustrated bygraph E in FIGURE 3.

From the foregoing description it will be apparent that the principle ofthe invention is to provide a control system for a dryer or the likewherein the initial heat input is at a reduced rate in comparison to theheat input capacity, followed by a modulated increase in heat inputeither up to or below capacity, followed by a modulated decrease in heatinput to a predetermined terminal amount. The method of drying providedby the principle of the invention is an improvement principally directedto a solution of the problem of synthetic fabric fusion and therefore itwill be further apparent that means such as a solenoid or electromagnet91 may be employed to deactivate lever 86 in the event it is desirableto provide a so-called normal drying cycle for the dryer wherein theinitial heat input is at maximum capacity. Such a cycle would proceed inthe manner of prior art modulated systems but would provide theadvantage of a selection of cycles having the shortest drying timeconsistent with safety to the fabrics being dried.

From the foregoing, it will be seen that the control system of thepresent invention provides an improved means for more careful control ofthe temperatures involved in various portions of a clothes dryer. Thesystem of the present invention is particularly applicable to the dryingof synthetic resin fabrics which have heretofore posed substantialdifiiculties in conventional dryers. While the invention has beendescribed in connection with a clothes dryer, it is equally applicableto other dryers and in particular to laundry appliances of thecombination washer-dryer type.

It should be evident that various modifications can be made to thedescribed embodiments without departing from the scope of the presentinvention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. The method of drying in a laundry appliance which includes the stepsof (1) driving a stream of air through a drying circuit including atreatment zone to assist in drying materials placed in the treatmentzone and directing gas fuel through a burner circuit for combustion at aburner located at one point in said drying circuit totemperature-condition the stream of air supplied to the treatment zone,

(2) applying a continuous biasing force to a metering device at onepoint in the burner circuit tending to allow full rate of flow of gasfuel through said burner circuit,

(3) counteracting said continuous biasing force with a first biasingforce regulated by a control device starting the initial flow of gasfuel at an intermediate rate of flow of gas fuel through said burnercircuit,

(4) removing said first biasing force to progressively increase the rateof supplying heat energy to the treatment zone and thereafter (5)counteracting said continuous biasing force with a second biasing forceregulated by a control device providing a terminal reduced rate of flowof gas fuel through said burner circuit to progressively decrease therate of supplying heat energy to the appliance,

(6) and regulating steps (4) and (5) as a function of the relative inletand outlet conditions of the air stream flowing through the treatmentzone.

2. The method of claim 1 and further characterized by controlling theremoval of said first biasing force in step (4) as a function of heatinput temperature into the treatment zone.

3. The method of claim 1 and further characterized by controlling theapplication of said second biasing force in step (5) as a function ofvariations in exhaust temperature from the treatment zone.

4. A heating system for a laundry appliance comprising means forming anair flow drying circuit including a treatment zone, air translatingmeans including air inlet and outlet means for driving a stream of airflowing through said treatment zone and a burner associated with saidair inlet means for adding heat energy to the air stream,

conduit means forming a fuel circuit through which a supply of gas fuelis driven to the burner for combustion,

valve means in said fuel circuit including a valve seat forming anopening through which the gas fuel flows and a valve head cooperablewith said seat for controlling the flow of gas fuel to the burner,

continuous biasing means loading said valve head towards an openposition,

a control device connected to said valve head and operable as a functionof the treatment zone exhaust temperature to counteract said continuousbiasing means and to progressively decrease the rate of supplying heatenergy to the treatment zone, and

a second control device connected to said valve head and having meansproducing a force to counteract said continuous biasing meanstemporarily at the start of a drying cycle to prevent opening of saidvalve head,

thereby to prevent excessive temperature build up in the treatment zonebefore said first control device is effective,

said second control device comprising,

a temperature sensor in the air inlet means, and translation meansbetween said sensor and said valve head to transmit from said sensor tosaid valve head as a function of variations of said air inlettemperature forces which are opposite to said counteracting means force.5. A heating system as defined in claim 4 and further characterized byauxiliary heating means on said temperature sensor for selectivelyheating said sensor as a part of a programmed drying cycle.

6. A heating system for a clothes dryer comprising a burner,

metering means including a metering orifice positioned to introduce afuel gas into said burner,

a valve means positioned for partial seating in said orifice to therebyregulate the fiow of gas through said orifice,

a spring urging said valve element away from seated relation with saidorifice,

a first temperature responsive means located in the exhaust from saiddryer,

means actuated by said first temperature responsive means to urge saidvalve element toward seated relation with said orifice,

a second temperature responsive element disposed in proximity to saidburner,

and means actuated by said second temperature responsive means to urgesaid valve element toward orifice opening position.

References Cited UNITED STATES PATENTS 2,142,042 12/1938 Bowdein et a1.3431 2,597,032 5/1952 Ray 15828 3,045,993 7/1962 Sidaris 26333 X3,132,853 5/1964 Fleer et al. 26333 3,191,917 6/1965 Pittendreigh 26333X FOREIGN PATENTS 926,061 5/1963 Great Britain.

FREDERICK L. MATTESON, IR., Primary Examiner. D. A. TAMBURRO, AssistantExaminer.

4. A HEATING SYSTEM FOR A LAUNDRY APPLIANCE COMPRISING MEANS FORMING ANAIR FLOW DRYING CIRCUIT INCLUDING A TREATMENT ZONE, AIR TRANSLATINGMEANS INCLUDING AIR INLET AND OUTLET MEANS FOR DRIVING A STREAM OF AIRFLOWING THROUGH SAID TREATMENT ZONE AND A BURNER ASSOCIATED WITH SAIDAIR INLET MEANS FOR ADDING HEAT ENERGY TO THE AIR STREAM, CONDUIT MEANSFORMING A FUEL CIRCUIT THROUGH WHICH A SUPPLY OF GAS FUEL IS DRIVEN TOTHE BURNER FOR COMBUSTION, VALVE MEANS IN SAID FUEL CIRCUIT INCLUDING AVALVE SEAT FORMING AN OPENING THROUGH WHICH THE GAS FUEL FLOWS AND AVALVE HEAD COOPERABLE WITH SAID SEAT FOR CONTROLLING THE FLOW OF GASFUEL TO THE BURNER, CONTINUOUS BIASING MEANS LOADING SAID VALVE HEADTOWARDS AN OPEN POSITION, A CONTROL DEVICE CONNECTED TO SAID VALVE HEADAND OPERABLE AS A FUNCTION OF THE TREATMENT ZONE EXHAUST TEMPERATURE TOCOUNTERACT SAID CONTINUOUS BIASING MEANS AND TO PROGRESSIVELY DECREASETHE RATE OF SUPPLYING HEAT ENERGY TO THE TREATMENT ZONE, AND A SECONDCONTROL DEVICE CONNECTED TO SAID VALVE HEAD AND HAVING MEANS PRODUCING AFORCE TO COUNTERACT SAID CONTINUOUS BIASING MEANS TEMPORARILY AT THESTART OF A DRYING CYCLE TO PREVENT OPENING OF SAID VALVE HEAD, THEREBYTO PREVENT EXCESSIVE TEMPERATURE BUILD UP IN THE TREATMENT ZONE BEFORESAID FIRST CONTROL DEVICE IS EFFECTIVE, SAID SECOND CONTROL DEVICECOMPRISING, A TEMPERATURE SENSOR IN THE AIR INLET MEANS, AND TRANSLATIONMEANS BETWEEN SAID SENSOR AND SAID VALVE HEAD TO TRANSMIT FROM SAIDSENSOR TO SAID VALVE HEAD AS A FUNCTION OF VARIATIONS OF SAID AIR INLETTEMPERATURE FORCES WHICH ARE OPPOSITE TO SAID COUNTERACTING MEANS FORCE.